A variety of techniques have been developed to remove oily films from particulate material and to separate oily material from particulate material and aggregates. Such methodology has been developed in conjunction with the removal of clays from particulate material, mineral fines from particulate material and the treatment of sands common to heavy oil production and tar sands production. Such techniques commonly involve a type of washing to remove the oily films and commonly involve the use of high intensity mechanical processes that are very demanding from a maintenance standpoint. In the field of heavy oil sands treatment, the most common techniques involve the use of washing tanks with mechanical mixing, followed by separation and dewatering using screw augers, centrifuges, cyclone separators and the like. This technology is inefficient in effecting a good separation of the contaminants including the sand particles and the developed slop oil emulsion. The processes are very labor intensive, require a high level of maintenance and hence in many applications are ineffective and uneconomical.
Looking to related industries, U.S. Pat. No. 5,160,605 describes a device for separating hydrocarbon products, such as cutting oils from water. A reasonably good separation is achieved by the use of settling tanks where the separated oil layer is skimmed by the use of a venturi pump to transport the skimmed oil to a second settling tank which is highly concentrated with hydrocarbon products. The water jet provides a convenient device for pumping the water and oil mix from one settling tank to the other.
U.S. Pat. No. 5,484,534 uses a venturi inductor to develop small bubbles of vapor which attach themselves to the oil and solid particles, thereby floating them to the surface and effect separation of the disbursed oil and solids from the water.
U.S. Pat. No. 4,783,268 describes the use of a micro-bubble generator which is used in the primary flotation/settling step of the hot water process to yield increased bitumen recovery. The micro-bubble generator involves the use of a jet nozzle which draws in a stream of air. The micro-bubbles are then generated in the mixing chamber to enhance the hot water process for extracting bitumen from mined oil sand.
U.S. Pat. No. 4,913,814 describes the use of jet pump mixing for mixing a liquid to be treated with another appropriate liquid to achieve solvent extraction. In order to enhance the solvent extraction process, the jet pumps are set up in a counter current cascade manner. The same stream is applied to the drive port of each jet pump in the cascade and the other flow stream is applied to the suction port of each jet pump in the cascade. The jet pumps in the cascade increase in size from a high pressure to a lower pressure end of the cascade so that the suction pressure required at successive jet pumps is reduced.
U.S. Pat. No. 4,424,112 described the use of a jet mixer in the solvent extraction of bitumen oils from tar sands. The jet mixer has an inlet into which the solvent soaked tar sands and hot water flow. The jet mixer is designed such that the pressure drop across the jet is sufficient to pulverize any rocks in the solvent soaked tar sands and that the total quantity of water entering the jet mixer is both mixed with the solvent soaked tar sands at the inlet. The slurry exiting the jet mixer continues the solvent extraction of the bitumen oils from the solid particles in the slurry. Due to the presence of solvent in the slurry, the temperature of the water is constrained so as to ensure that the solvent is not driven off from the solvent soaked tar sands. The jet mixer also serves the purpose of transferring the solvent soaked tar sands directly from one tank to a bitumen extract separator.
An article published in Quarry Management, February 1993 by A. W. Wakefield, entitled "The Jet-Pump Scrubber" describes a system for removing clay particles from the surfaces of sand particles. The jet pump scrubber is operated to produce vapor bubbles in the jet stream. The bubbles collapse at the surfaces of the sand particles to cause a shockwave in the sand particles due to cavitation in the mixing chamber and thereby remove clay particles from the sand surfaces. This action may be used to remove, for example, iron particles from the surfaces of larger particulate materials.
None of the above processes contemplate the application of jet pump scrubber technology in the removal of oily films from particles particularly sand particles, other than by solvent extraction. In accordance with this invention, applicant has found quite surprisingly that jet pump scrubber technology may be used to remove the oily film from the surfaces of particulate materials when the jet pump scrubber is operated under particular conditions and within a tank which provides for recirculation of the particles for retreatment in the jet pump scrubber.